The following disclosure relates to a fire protection system for rack storage, and in particular, to an in-rack sprinkler system capable of protecting exposed, expanded and unexpanded, plastics.
Rack storage is a conventional storage arrangement used in various industries and facilities. As provided in Section 3.9.3.7 of the U.S. National Fire Protection Association Standard 13 (NFPA 13) (2007 Ed.), a “rack” is “[a]ny combination of vertical, horizontal, and diagonal members that supports stored materials. Shelving in some racks can be solid, slatted, or open. Racks can also be fixed, portable, or movable. Loading commodities can be either manual—using lift trucks, stacker cranes, or hand placement—or automatic—using machine-controlled storage and retrieval systems.” Conventionally, a commodity 102 to be protected is placed on a pallet 104 and the commodity 102 and the pallet 104 are stored together on a shelf 106 in a rack 108, as shown in FIG. 1A.
Racks can be single row, double row, or multiple row, with or without solid shelving. The terms “single row”, “double row”, and “multiple row” refer to the depth of the rack configuration in terms of the number of pallets that can be stored back to back. For example, a double row rack 108 has a depth that can accommodate two pallets back to back, as shown in the end elevation view of the schematic shown in FIG. 1B. When the palletized commodities 102 are stored apart from one another in the racks 108, 108 the spaces formed between the palletized commodities 102 form transverse flue spaces 112, as shown in FIGS. 1A and 1C. Also, the vertical spaces between adjoining racks 108 (i.e., between the backs of rows of storage) form what are known as longitudinal flue spaces 114 (FIGS. 1B and 1C). An isometric view of a conventional double row rack 108 showing the relationship of various parameters is shown in FIG. 2. As shown in FIGS. 3A and 3B, double and multiple-row racks 108 are conventionally spaced apart from other double or multiple-row racks 108 by an aisle width 118, which is conventionally 4 or 8 feet (1.22 to 2.44 meters). FIGS. 3A and 3B also show, respectively, a plan view and an end elevation view of two double row rack arrangements 108 separated by an aisle having an aisle width 118.
Fire protection sprinklers are conventionally connected to a conduit to receive pressurized fire-extinguishing fluid, such as water. A typical fire protection sprinkler has a base with a threaded portion for connection to the conduit, and an output orifice to output the fire-extinguishing fluid to provide fire control and/or fire suppression. The output orifice is sealed by a seal cap that is held in place by a release mechanism. The release mechanism is designed to release the seal cap under predetermined conditions, thereby initiating the flow of the fire-extinguishing fluid. A typical release mechanism includes a thermally-responsive element, e.g., a frangible bulb or fusible link, and may also include a latching mechanism.
Certain conventional fire protection sprinklers have a pair of arms that extend from the base portion and meet at a hub portion to form a frame. The hub portion is spaced apart from the output orifice of the base portion and is aligned with a longitudinal axis of the base portion. The hub portion may have a set-screw configured to apply a pre-tension force to the release mechanism. A deflector may be mounted on the hub, transverse to the output orifice, to provide dispersion of the output fire-extinguishing fluid.
Fire protection sprinklers may be mounted on a fluid conduit running along a ceiling and may either extend downward from the conduit, referred to as a “pendent” configuration, or may extend upward from the conduit, referred to as an “upright” configuration. Alternatively, fire protection sprinklers may be mounted on a wall, a certain distance below the ceiling, referred to as a “horizontal sidewall” configuration. An output orifice of a horizontal sidewall sprinkler is oriented so that the fire-extinguishing fluid is output horizontally and sprays onto an area to be protected in front of the sprinkler.
An “extended coverage storage sprinkler (specific application),” as described in Section 55.1 of the Standard for Automatic Sprinklers for Fire-Protection Service, published by Underwriters' Laboratories, 11th Ed., Nov. 4, 2005 (UL199) is a sprinkler that is intended to be installed using the extended coverage area up to 196 square feet (e.g., 14 ft by 14 ft) (18.21 square meters) (e.g., 4.27 meters by 4.27 meters), and using specific application criteria specified in NFPA 13. These extended coverage storage sprinklers (specific application) incorporate a heat responsive element and release mechanism that has a response time equal to or less than that of a standard response sprinkler used on sprinklers designed for standard spacings up to 100 square feet (e.g., 10 ft by 10 ft) (9.29 square meters) (3.05 meters by 3.05 meters). Extended coverage sprinklers are installed in accordance with Section 8.8.2 of NFPA 13.
NFPA 13 defines a number of different types of storage sprinkler configurations and protection criteria. Fire protection systems that provide fire protection for commodities stored in storage racks conventionally s include sprinklers that are arranged within the storage racks, i.e., in-rack sprinklers, that may be disposed directly above the commodity stored on a shelf of the storage rack. Section 8.13 of NFPA 13 specifies installation requirements for in-rack sprinklers and section 8.13.2.2 of NFPA 13 requires that in-rack sprinklers be ordinary-temperature, standard response or quick response sprinklers and have a nominal K-factor of 5.6 or 8.0 gpm/(psi)1/2.
Chapter 13 of NFPA 13 describes in-rack sprinkler configurations for various classifications of commodities for storage heights up to 12 feet (3.66 meters). According to section 13.3.2 of NFPA (2007 Edition), in-rack sprinklers shall have a K-factor of 5.6 gpm/(psi)1/2 or greater, and shall operate at a minimum of 15 psi (1 bar). Table 13.2.1 and FIG. 13.2.1 of NFPA 13, Chapter 13 specify the maximum ceiling height, maximum storage height, area of sprinkler operation, and discharge density for various hazard classes and storage types for in-rack sprinkler installations for storage up to 12 feet (3.66 meters) in height. Section 16.2 of NFPA 13 provides “Protection Criteria for Rack Storage of Class I Through Class IV Commodities Stored Up to and Including 25 ft in Height,” Section 16.3 provides “Protection Criteria for Rack Storage of Class I Through Class IV Commodities Stored Over 25 ft in Height,” and Chapter 17 provides “Protection of Plastic and Rubber Commodities That are Stored on Racks.”
Fire protection of rack storage configurations poses a number of challenges. Fire sprinkler systems are usually required to be installed in warehouses and other similar article storage areas. Conventional sprinkler systems are generally installed in the ceiling of the building and the sprinklers spray water in the area of the fire to either control and/or to extinguish the fire. In storage areas including racks, however, a fire that starts on a lower rack is shielded from the spray emanating from a sprinkler positioned above the rack, either by shelving above the rack or by commodities stored above the rack. This factor is significantly aggravated as the number of shelves is increased. Moreover, in cases in which sprinklers are located in the ceiling above a given rack, a fire in lower shelves of the rack may not actuate the heating-actuated sensing elements of the sprinklers in a sufficiently short amount of time to provide effective control of the fire. And, as noted, even when the sprinklers of the fire sprinkler system are actuated, the fire on the lower shelves is protected from the spray by upper shelves, and thus, the fire can spread upwardly.
In particular, early suppression-fast response (ESFR) sprinklers and control mode special application (CMSA) sprinklers have been used as ceiling level sprinklers in place of in-rack sprinklers. Conventional ESFR and CMSA sprinklers must operate at a relatively high pressure and discharge relatively large volumes of water in order to provide the same level of fire protection as the in-rack sprinklers they replace. The increased water demand and higher operating pressure required by ESFR and CMSA sprinklers, however, are generally undesirable consequences. Moreover, ESFR and CMSA sprinklers are not approved for the protection of all storage commodities and commodity storage configurations. Furthermore, ESFR and CMSA sprinklers are limited for use based on building heights.
Overhead or roof sprinkler systems supplemented by intermediate levels of sprinklers have been suggested, including, for example, sprinklers mounted within the storage racks, and also within aisles between racks (e.g., U.S. Pat. No. 3,732,930 (D'Anneo)). This arrangement was not generally satisfactory because consistent, timely, and dependable detection and sprinkler actuation was not achievable. Consequently, greater damage to stored material, and greater risk to the stored commodity and the building structure, prevented widespread use of this arrangement in high storage facilities. Moreover, installing sprinklers within storage racks increases the cost and complexity of the sprinkler system, and reduces the flexibility of locating and relocating storage racks due to the fixed positions of the sprinkler plumbing. Also, because commodities may be routinely moved in and out of the storage racks, there is an increased risk of damage to the in-rack sprinklers from such handling of the commodities.
Also, fire protection systems using foam have been suggested for use in high-rise storage facilities. Generally, such a system has a foam generator coupled with a suitable sensing system that is capable of filling an entire building volume with a light foam. Single generators capable of producing as much as 2,000 cubic feet per minute (56.63 cubic meters per minute) of foam are available. The time required for filling the building varies, but generally ranges from two to eight minutes. Such systems are not completely satisfactory because the foam may damage goods (i.e., commodities) stored within the facility. Also, when the fire occurs at a high elevation, the foam may not reach the height where the fire is located for some time, permitting the fire to spread to the roof or ceiling and become out-of-control. Further, the foam system mentioned in the D'Anneo patent is relatively expensive, requires great quantities of water, and requires a good deal of maintenance, and the generators, which are heavy and are normally mounted on the roof, may result in structural damage if insufficient reinforcement is provided. In addition, removal of the foam from the warehouse after the fire is extinguished is a problem.